An important prerequisite for the cooling effect of a cooling tower is even spraying of cooling water to the water spraying filler in the cooling tower. A water spraying approach in cooling tower is implemented with numerous non-pressure water spraying nozzles 3 with the same aperture 2, which are evenly distributed on the bottom of a water distribution channel 1 (as shown in FIG. 1); even water distribution from the nozzles is a prerequisite for even water spraying on the entire cross section and high water spraying efficiency. In the troughing distribution channel, the incoming water is distributed from the middle part towards the two ends of the channel, when the water inflow is relatively low (e.g., water inflow≦water spraying yield), the influent in the middle part will flow away through the spraying nozzles near the water inlet before it is distributed to the two ends of the channel; as a result, there will be no water or insufficient water at the two ends of the water distribution channel in the axial direction. The bigger the cooling tower structure is, the more severe the phenomenon will be. Consequently, the heat exchange area between chilled hot water and air will be reduced, and the heat exchange efficiency of the cooling tower will be degraded and lower than the design efficiency. In practice, a solution is to utilize sprinklers or sprinkler interfaces with different apertures according to the water inflow, so as to ensure even water distribution to the nozzles, however, that solution is troublesome, because the water inflow into the cooling tower varies frequently in practice, particularly in the cases that a plurality of cooling towers are used in combination and the nozzles are in a large quantity. Actually, it is impractical to replace the nozzles according to the water inflow.
Prior art target-type sprinklers have a flow regulation ring, which is used to achieve even water distribution at nozzles with different flow rates. See, for example, the split down-regulation target-type sprinkler disclosed in Chinese Patent CN2175391, which adds a nozzle or pipe joint with threaded connection between the deflector ring and the deflector of the existing target-type sprinkler; and the height-adjustable target-type sprinkler disclosed in Chinese Patent CN2143759, which adds a flow regulator on the existing target-type sprinkler by threaded connection in the flow regulation ring, and in which the flow regulator comprises a deflector ring with a male thread cylindrical body and a louver-form structure on the top, and grid shaped openings on the sides. A main object of the above-mentioned inventions is to keep a constant water inflow level for the nozzles against severe floor level differences and thereby ensure even water distribution in the towers. However, such solutions can't deal with dynamic variations of the water field, because they can't ensure even water distribution at different water inflow rates automatically, and it is impractical to carry out manual regulation frequently in engineering applications. Moreover, such structures will cause increased manufacturing cost of the nozzles.